Electronic assembly with hot spot cooling

Abstract

A composite of two or more thermal interface materials (“TIMs”) is placed between a die and a heat spreader to improve cooling of the die in an integrated circuit package. The two or more TIMs vary in heat-dissipation capability depending upon the locations of die hot spots. In an embodiment, a more thermally conductive material may be positioned over one or more die hot spots, and a less thermally conductive material may be positioned abutting and/or surrounding the more thermally conductive material. The two or more TIMs may comprise a solder and a polymer. The composite TIM may be preformed as one unit or as a plurality of units. Methods of fabrication, as well as application of the package to an electronic assembly and to an electronic system, are also described.

1. An integrated circuit package comprising:
 a substrate having at least one die on a surface thereof; 
 a heat spreader positioned over the at least one die, the heat spreader having a surface area larger than a surface area of the at least one die; and 
 a thermal interface material positioned between the heat spreader and the at least one die, the thermal interface material varying in composition according to its X-Y location, wherein the thermal interface material comprises solder positioned over die hot spots, and wherein the thermal interface material further comprises a polymer material abutting the solder. 
 
   
   
     2. The package recited in  claim 1 , wherein the composition of the thermal interface material varies according to the die hot spots. 
   
   
     3. The package recited in  claim 1 , wherein the thermal interface material comprises at least two materials having different thermal characteristics. 
   
   
     4. The package recited in  claim 1 , wherein the polymer is from the group consisting of a phase-change polymer, a gel-type polymer, a grease-type polymer, and a high cross-linked elastomer. 
   
   
     5. The package recited in  claim 1 , wherein the polymer comprises thermally conductive metallic or ceramic particles. 
   
   
     6. The package recited in  claim 1 , wherein the polymer is positioned over regions of the at least one die that are relatively cooler than the die hot spots when the die is in operation. 
   
   
     7. The package recited in  claim 1 , wherein the polymer material surrounds the solder. 
   
   
     8. An electronic assembly comprising:
 at least one integrated circuit package having
 a substrate; 
 at least one die positioned on a surface of the substrate; and 
 a lid positioned over the at least one die; and 
 
 a thermal interface material placed between the lid and the at least one die, the thermal interface material having two or more regions of differing composition, wherein at least one of the regions comprises a solder region positioned over at least one die hot spot and wherein at least one of the regions comprises a polymer region abutting the solder region. 
 
   
   
     9. The assembly recited in  claim 8 , wherein the thermal interface material comprises a plurality of polymers. 
   
   
     10. The assembly recited in  claim 8 , wherein the at least one polymer region is positioned over a region of the at least one die that is relatively cooler than the die hot spots when the die is in operation. 
   
   
     11. A structure comprising:
 a composite thermal interface material comprising two or more regions of differing composition, wherein at least one of the regions comprises a solder region to be positioned over at least one die hot spot, and wherein at least one of the regions comprises a polymer region abutting the solder region. 
 
   
   
     12. The structure recited in  claim 11 , wherein the composite thermal interface material comprises solder and a polymer, wherein the polymer is from the group consisting of a phase-change polymer, a gel-type polymer, a grease-type polymer, and a high cross-linked elastomer. 
   
   
     13. The structure recited in  claim 11 , wherein the composite thermal interface material is preformed either as one unit or as a plurality of units.